exhaust dimension
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 3,010
Likes: 1
From: Sweden/Stockholm
exhaust dimension
Hi
Im about to build the exhaust for my "new" engine.
Se sign for my mods.
I got hooker headers, and hooker front ypipe.
From the front ypipe i got a strait 3 inch pipe instead of the cat.
Then I look at the magnaflow catback to end the exhaust. http://www.magnaflow.com/02product/parts/15658_lg.jpg.
Im a bit worried that the center 3 inch pipe is going to kill flow to much. ( Going from dual 3 inch to a singel )
As I dont have a good exhaust builder around the corner where I live I would like to keep it simple.
Hope you can guide me.
Im about to build the exhaust for my "new" engine.
Se sign for my mods.
I got hooker headers, and hooker front ypipe.
From the front ypipe i got a strait 3 inch pipe instead of the cat.
Then I look at the magnaflow catback to end the exhaust. http://www.magnaflow.com/02product/parts/15658_lg.jpg.
Im a bit worried that the center 3 inch pipe is going to kill flow to much. ( Going from dual 3 inch to a singel )
As I dont have a good exhaust builder around the corner where I live I would like to keep it simple.
Hope you can guide me.
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
A 3" pipe will flow about 800cfm and you need about 2.2cfm for 1chp. At 2.0cfm of flow per chp expect to lose maybe 1-2% of hp due to back pressure.
So your 3" exhaust system will flow to about 360chp before back pressure takes off a little hp. And of course each muffler must flow about 400cfm.
Of course true 2 1/2" duals (flowing ~1,100cfm or 500chp) will do a better job than a single 3" cat-back system.
But since your heades go into a 3" front Y don't worry about 3" pipe after that.
Any simulation I've done on Dyno2000 software simulator shows best power with open headers as opposed to headers with hi-flow mufflers. So indeed back pressure is our enemy, though it may not take off much power.
How much HP do you expect to make at the crank?
So your 3" exhaust system will flow to about 360chp before back pressure takes off a little hp. And of course each muffler must flow about 400cfm.
Of course true 2 1/2" duals (flowing ~1,100cfm or 500chp) will do a better job than a single 3" cat-back system.
But since your heades go into a 3" front Y don't worry about 3" pipe after that.
Any simulation I've done on Dyno2000 software simulator shows best power with open headers as opposed to headers with hi-flow mufflers. So indeed back pressure is our enemy, though it may not take off much power.
How much HP do you expect to make at the crank?
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 3,010
Likes: 1
From: Sweden/Stockholm
thanks for the reply 
My goal is 400hp at the crank (+-15hp)
So what you saying is that due to my 3 inch front ypipe, the strait singel 3" pipe should not hold me back to much?
My goal is 400hp at the crank (+-15hp)
So what you saying is that due to my 3 inch front ypipe, the strait singel 3" pipe should not hold me back to much?
Originally Posted by 65Z01
A 3" pipe will flow about 800cfm and you need about 2.2cfm for 1chp. At 2.0cfm of flow per chp expect to lose maybe 1-2% of hp due to back pressure.
So your 3" exhaust system will flow to about 360chp before back pressure takes off a little hp. And of course each muffler must flow about 400cfm.
Of course true 2 1/2" duals (flowing ~1,100cfm or 500chp) will do a better job than a single 3" cat-back system.
But since your heades go into a 3" front Y don't worry about 3" pipe after that.
Any simulation I've done on Dyno2000 software simulator shows best power with open headers as opposed to headers with hi-flow mufflers. So indeed back pressure is our enemy, though it may not take off much power.
How much HP do you expect to make at the crank?
So your 3" exhaust system will flow to about 360chp before back pressure takes off a little hp. And of course each muffler must flow about 400cfm.
Of course true 2 1/2" duals (flowing ~1,100cfm or 500chp) will do a better job than a single 3" cat-back system.
But since your heades go into a 3" front Y don't worry about 3" pipe after that.
Any simulation I've done on Dyno2000 software simulator shows best power with open headers as opposed to headers with hi-flow mufflers. So indeed back pressure is our enemy, though it may not take off much power.
How much HP do you expect to make at the crank?
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 3,010
Likes: 1
From: Sweden/Stockholm
Originally Posted by 65Z01
That's right; the air must slow down some to enter the 3" pipe so if the pipe is 1' or 6' long really doesn't matter much.
I would love to have dual 3 inch all the way. But as I said, im not close to a exhaust shop. And I already got the front ypipe, and the magnaflow. So this would be the most easy sollution for me. But I whas worried that not using true 3 inch dual exhaust would hold me back to much ( 50-60 hp ).
I really hope I can get close to my goal ( 400 chp ).
Perhaps anyone knows how much the magnaflow flows??
Race Director
Joined: Dec 2002
Posts: 13,348
Likes: 233
From: SCMR Rat Pack'r Charter Member..Great Bend KS
Old wives tale.
Any back pressure hurts power.
Think about it; all back pressure does is prevent the most efficient expulsion of exhaust gas. How does that help power?
(power being torque, which is measurable. horsepower in and of itself is not measurable...it is a calculation)
Larry
Any back pressure hurts power.
Think about it; all back pressure does is prevent the most efficient expulsion of exhaust gas. How does that help power?
(power being torque, which is measurable. horsepower in and of itself is not measurable...it is a calculation)
Larry
Melting Slicks
Joined: Jun 2004
Posts: 3,032
Likes: 4
Originally Posted by code5coupe
Old wives tale.
Any back pressure hurts power.
Think about it; all back pressure does is prevent the most efficient expulsion of exhaust gas. How does that help power?
(power being torque, which is measurable. horsepower in and of itself is not measurable...it is a calculation)
Larry
Any back pressure hurts power.
Think about it; all back pressure does is prevent the most efficient expulsion of exhaust gas. How does that help power?
(power being torque, which is measurable. horsepower in and of itself is not measurable...it is a calculation)
Larry
from what I've learned: The header primaries are the important piece to maintaining torque curves. The exhaust just needs to flow.
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